1. Field of the Invention
This invention relates to supports for rolls of material.
In many different types of apparatus a roll of flexible material such as paper has to be supported on a rotatable shaft. Particularly in the case of paper, the roll is normally wound on a tube which may consist, for example, of cardboard or of a synthetic resin material. In some cases the tube may be allowed to rotate freely on the shaft, for example while material is paid off from the roll.
2. Description of the Prior Art
In the past, when it has been necessary for the roll of material to rotate with the shaft, various different methods have been used to lock the tube to the shaft. In one system, end cheeks have been provided on the shaft and these have been urged towards each other to grip the ends of the tube, either by means of a spring or by means of a positive compression device such as a screw. In other systems a slot has been provided in one or both ends of the tube and this slot has engaged with a corresponding ridge on the cheek or cheeks. In yet another system, spring means have been provided on the shaft itself to grip the interior of the tube. These have frequently been unsatisfactory because of variations in the internal diameter of the tube. Also difficulty has sometimes been experienced in mounting the tube on an axle provided with spring means, in that the spring has caught in the interior of the tube, particularly in the case of cardboard tubes.
It is an object of the present invention to provide a system for supporting a roll of material on a shaft, which system avoids the disadvantages of the known systems.
In accordance with the invention the shaft includes at least two portions, one of which is internally threaded to receive an externally threaded boss on one end of the other portion so that the two portions can be assembled coaxially. The boss carries an annular elastomeric member, the external diameter of which, when the two portions are not assembled, is less than the internal diameter of the roll, whereas, when the two portions are assembled, pressure on the annular member from the adjacent ends of the two shaft portions increases its external diameter at least to the internal diameter of the roll.
It is to be understood that in this definition of the invention the word "roll" is being used to refer both to an unsupported roll of material and also to a roll of material supported on a tube. Thus in the case of a roll supported on a tube, the internal diameter referred to in the preceding paragraph is the internal diameter of the tube.
The elastomeric material of the annular member is preferably natural or synthetic rubber, but may be any other suitable material which, when compressed axially, will expand radially and will return to its initial dimensions when the axial pressure is removed.
In some cases, and especially when the axial length of the roll is relatively large, it will be desirable to provide two or more elastomeric annular members in the shaft so that the gripping pressure is applied evenly along the length of the interior of the roll or the tube on which it is mounted In such cases the shaft is of course divided into the appropriate number of portions to accommodate the required number of annular members.